Selectivity of Ion Exchange on Iminocarboxyl Resin and the Hydration Energy of Its Ionic Forms

Abstract

Characteristics of the hydration of macroporous iminodicarboxyl ion-exchange resin in the protonated, sodium, copper, and nickel forms are determined, and the Gibbs energy of hydration and its change upon transitioning from the initial ionic form to the ion-sorbed form are calculated. The way of calculating the Gibbs energy of the interfacial transfer of a solvent during the ion-exchange process is substantiated. It is established that the selectivity of an ion-exchange resin in the functional form toward the extracted transition-metal cations depends not only on the mean amount of solvent per functional group of the polyampholite, but also on the change in sorbent hydration during the ion exchange. The contribution determining the selectivity of copper(II) and nickel(II) cations toward iminodicarboxyl ion-exchange resin is an ion-exchange component with the formation of ionite complexes. In addition, the change in hydration (being an energetically advantageous process) facilitates sorption as a whole.